Robotic arm

ABSTRACT

A robotic arm includes a first link and a first joint. The first link has internal link cables extending from one end to an opposed end thereof. The first joint is operably connected to the first link at one end thereof. The first joint has a hollow drive shaft, an off axis drive  121  and a first joint motor and first joint internal cables extending through the hollow drive shaft. The link cables and the first joint cables are operably connected. The robotic arm may further include a second joint operably connected to the first link. The second joint module has an active side, a passive side with electronic connectors, second joint internal cables, and a second joint motor and the active side is mechanically connected to the link and the electronic connectors of the passive side are operably connected to the link cables.

FIELD OF THE DISCLOSURE

This disclosure relates to robotic arms and in particular robotic armswith internal cables.

BACKGROUND

Robot joints used in robotic arms are well known. However, when jointsand arms are to be used in certain applications constraints areintroduced in the specifications that are not generally present ingeneral applications. For example the payload to weight ratio is veryimportant in space and planetary applications and mobile robotapplications. As well, size constraints may be very important inmanufacturing and mobile robot applications. Any design of modern robotneeds to consider: low weight, high payload, long reach, kinematicdexterity, high accuracy and repeatability, and low cost.

Accordingly most of the above considerations can be addressed by thecombination of two joints in a single module which would be advantageousover separate first joint and second joints. A combination two jointmodule may provide advantages in regard to a compact size, low weight,high payload, and high accuracy and repeatability. Such joints areparticularly useful in robotic arms. As well, modular robotic armshaving internal cables are advantageous over conventional robotic arms.

SUMMARY

A two joint module includes a module housing, a first joint and a secondjoint. The module housing has a structural support portion. The firstjoint has a first motor and a first motor axis and a first joint axis.The second joint has a second motor and a second motor axis and a secondjoint axis. The second joint axis is at an angle to the first jointaxis. The first joint is attached to the structural support portion andthe second joint is attached to the structural support portion.

The first joint may be a pitch joint. The second joint may be one of aroll joint and a yaw joint. The second joint may be a prismatic joint.

The second motor may be perpendicular to the second joint axis. Thefirst motor axis and the first axis may be parallel.

Each joint may include a gearhead and a drive operably attached to therespective motor. The drive may be a harmonic drive. Each motor mayinclude absolute encoders and incremental encoders. Each motor may becapable of measuring speed and current. The two joint module may includetorque sensors. Each joint of the two joint module may be a low power,high torque joint.

One of the first and second motor may be include angled gearing such thesecond joint axis is at an angle to the first joint axis. The firstjoint axis may be orthogonal or at right angles to the second jointaxis. The right angle gearing may be one of a worm gear and a hypoidgear.

The module housing may act as an electromagnetic shield. The modulehousing may include a module housing box and each motor may be externalto the module housing box. The module housing may include motor housing.

The first joint and second joint may be configured to be reversible.

Each motor may be operably connected to cables that are internal to themodule housing. One of the first joint and second joint may have anactive side and a passive side of the housing and the other of the firstjoint and second joint may have a hollow central axis and the cables maypass through the passive side of the housing of one joint and the hollowcentral axis of the other joint.

A two joint module includes a module housing, a first joint and a secondjoint. The first joint has a passive side and an active side and has afirst motor. The second joint has a hollow central axis and an off axisdrive and has a second motor. Internal cabling runs through the passiveside of the first joint and through the hollow central axis of thesecond joint.

Each joint may include electronics and the electronics are capable ofbeing connected in series and the cables are operably connected to theelectronics and operably connected to the motors.

The first motor and gearhead may be a combination motor and gearhead.The harmonic drive may be internal to the combination motor andgearhead.

A robotic arm includes a first link and a first joint. The first linkhas internal link cables extending from one end to an opposed endthereof. The first joint is operably connected to the first link at oneend thereof. The first joint has a hollow drive shaft, an off axis driveand a first joint motor and first joint internal cables extendingthrough the hollow drive shaft. The link cables and the first jointcables are operably connected.

The robotic arm may further include a second joint operably connected tothe first link. The second joint module has an active side, a passiveside with electronic connectors, second joint internal cables, and asecond joint motor and the active side is mechanically connected to thelink and the electronic connectors of the passive side are operablyconnected to the link cables.

The robotic arm may further include a second link operably connected toone of the first joint and the second joint. The first joint and thesecond joint may be a combination two joint module.

The robotic arm may further including a third joint and a fourth jointeach operably connected to the second link. The third joint and thefourth joint may be a combination two joint module.

The robotic arm may further include a fifth joint and a sixth joint. Thefifth joint and the sixth joint may be a combination two joint module.

Further features will be described or will become apparent in the courseof the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will now be described by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of a two joint modulewhich may be used as a wrist joint;

FIG. 2 is a blown apart view of the two joint module of FIG. 2

FIG. 3 is cross sectional view of the two joint module of FIG. 2 takenalong line 3-3

FIG. 4 is a cross sectional view of the two joint module of FIG. 2 takenalong line 4-4;

FIG. 5 is a perspective view of an alternate embodiment of a two jointmodule which may be used as an elbow joint;

FIG. 6 is perspective view of an alternate embodiment of a two jointmodule which may be used as a shoulder joint;

FIG. 7 perspective view of an alternate embodiment of a two joint modulesimilar to that show in FIG. 6 but also including a fork connector;

FIG. 8 is a perspective view of an arm assembly including the two degreeof freedom joins shown in FIGS. 1, 5 and 7;

FIG. 9 is a perspective view of an alternate embodiment of a two jointmodule;

FIG. 10 is a top view of the two joint module of FIG. 9;

FIG. 11 is a side view of the two joint module of FIG. 9;

FIG. 12 is a front view of the two joint module of FIG. 9;

FIG. 13 is a blown apart view of the two joint module of FIG. 9;

FIG. 14 is a cross sectional view of the two joint module of FIG. 9;

FIG. 15 is a blown apart view of a two joint module which includes aroll joint and a prismatic joint;

FIG. 16 is a perspective view of an arm including the two joint modulesof FIGS. 9 and 15; and

FIG. 17 is a perspective blown apart view of the arm of FIG. 16.

DETAILED DESCRIPTION

Referring to FIGS. 1 to 4, a two joint module is shown generally at 10.Module 10 includes a first joint 12, a second joint 14 and a modulehousing 16. The first joint 12 has a first joint axis 28 and the secondjoint 14 has a second joint axis 46 and the first axis 28 is generallyorthogonal to the second axis 46. However, the angle between the twojoints need not be orthogonal rather it could be at another angledepending on the design constraints. Typically the first joint is apitch joint and the second joint is a roll joint or yaw joint.

The first joint 12 includes a first motor 18, a first gearhead 20 and afirst drive 22. By way of example the first drive 22 is a harmonicdrive. The first motor 20 and first gearhead 18 may be incorporated inthe same unit 24 as shown herein. The first motor and gearhead may alsoinclude an incremental encoder 21. The motor gearhead is a speed reducerto reduce the power required to operate the first module. The gearheadhas a reduction ratio of 20584:1. The use of the gearhead provides forthe option to use smaller, lighter and lower power motors. Theincremental encoder 21 measures relative rotational position of themotor and in turn by determining the rate of change of the rotationalposition the speed of the motor is determined. The position of the motoris determined prior to the gearhead. The first drive 22 may include anintegrated torque sensor 23 which measures the output torque that isapplied after all of the gearing. The first joint also includes anabsolute encoder 26 which determines the rotational position of theoutput after all of the gears. The absolute encoder is used to determinethe relative rotational position of the outer link with respect to theinner link.

The first joint 12 has a first motor axis and a first joint axis 28. Thefirst motor 20, first gearhead 18, first drive 22 and first absoluteencoder 26 are concentric with the first joint axis 28.

The second joint 14 includes a second motor 32, a second gearhead 30 anda second drive 34. The second motor or drive 34 may be a harmonic drive.The second motor 32 and second gearhead 30 may be incorporated in thesame unit 36 as shown herein. The second motor and gearhead may alsoinclude an incremental encoder 31. The incremental encoder 31 measuresrelative rotational position of the motor and from the rate of change ofthe relative rotational position the speed of the motor is determined.The position of the motor is determined prior to the gearhead. Thesecond drive 34 may include an integrated torque sensor 35 whichmeasures the output torque that is applied after all of the gearing. Thesecond joint also includes an absolute encoder 38 which determines therotational position of the output after all of the gears. The absoluteencoder is used to determine the rotational position of the link.

The second joint 14 includes a hollow drive shaft 40 and angled gearingthat allows for internal cabling 41. A worm gear 42 and worm 44 connectthe second motor and gearhead combination 36 to the drive shaft 40. Thisallows the second motor 32, the second motor axis and gearheadcombination 36 to be positioned at an angle to the second joint axis 46.The angle may be perpendicular but it will be appreciated by thoseskilled in the art that the different angles may be chosen depending onthe design constraints for the joint. The positioning of the motor andgearhead combination 36 in this fashion allows for a compact two jointmodule.

The second joint 14 has a second joint axis 46. The second drive 34,second absolute encoder 38 and hollow drive shaft 40 are concentric withthe second axis 46. The second drive 34 may be a harmonic drive. Thesecond drive or motor 34, second motor axis and gearhead combination 36are perpendicular to second joint axis 46. The second motor axis of thesecond motor and gearhead combination 36 is parallel to the first motoraxis of the first motor and gearhead combination 24.

Electronic modules 48 are operably connected to each of the first joint12 and the second joint 14. The electronic modules 48 are operablyconnected to a control unit (not shown). The electronic modules 48receive information from the control unit in regard to the desiredmovement of the joint and control the first motor 18 and second motor 30accordingly. Each electronic module 48 includes a torque sensoramplifier to increase strength of the output signal from the torquesensors. Each electronic module 48 includes interfaces for all of thesensors such as the incremental encoders, absolute encoder, and outputfrom torque sensor amplifier, and is capable of digitizing all sensorinformation. Each electronic module 48 includes power connections.

The module housing 16 includes a first housing cover with electronicconnections 53. A first output plate 50 is operably attached to theoutput of the first drive 22. The output plate 50 is adapted formechanical external connections and is movable relative to the modulehousing 16 and output plate 50 is the active side of the housing. Thefirst housing cover 52 with electronic connections 53 is for the jointmodules interfaces for power and communications and is used forpositioning the link which is attached to the module 10 and firsthousing cover is the passive side of the housing. The second joint 14has a combined second output plate 54 and electronic connections 55. Theactive first output plate 50, passive first housing cover withelectronic connections 53 and the second output plate, together with thehollow drive shaft 40 of the second joint 14 allows for internalcabling. However it will be appreciated that the first joint could havea hollow drive shaft and the second joint could have an active and apassive side. The module housing 16 also includes a housing box 56. Themodule housing box 56 is robust enough to transmit forces and torquesand the module housing box is a structural support portion and firstjoint 12 and second joint 14 are attached thereto. As well, the modulehousing 16 enclosures the electronics and motors and protects them fromexternal environment. The module housing 16 acts as an electromagneticshield. The module housing 16 is made from metal and is conductive. Theelectronics modules 48 are enclosed by the housing 16. The housing 16provides electromagnetic shielding.

The embodiments of the two joint module 10 shown in FIGS. 1 to 4 are fora small relative to the other joints shown in arm 70 in FIG. 8 and jointmodule 10 may be used as a wrist module. FIG. 5 shows a medium sizedembodiment of a two joint module 60 which is similar to that shown inFIGS. 1 to 4 but is somewhat larger and may be used as an elbow module.Since the elbow joint 60 has a greater distance from the payload, theelbow joint 60 is required to generate greater torques and thus requireslarger motors and drives. FIG. 6 show a larger sized embodiment of a twojoint module 62 that is similar to modules 10 and 60 but larger and maybe used as a shoulder module. FIG. 7 is a larger module similar to thatshown in FIG. 6 but further including a fork connector 64. Joint module62 includes larger motors and drives than those of modules 10 and 60 andcan generate higher torques. The electronics are configured so that thejoint described herein with internal cabling are capable of beingconnected in series.

By way of example only the chart below shows the torques that can begenerated by the specific joints shown herein. It will be appreciatedthat the motor size and gear ratios can be varied to achieve thespecific torque that is required for a specific application.

MOTOR POWER JOINT (W) GEAR RATIO TORQUE Module 62 Shoulder First Joint50 35652:1 826 Shoulder Second 25 39243:1 367 Joint Module 60 ElbowFirst Joint 25 37226:1 334 Elbow Second Joint 5 23085:1 71 Module 10Wrist First Joint 5 20584:1 65 Wrist Second Joint 5 21309:1 42

As is well known in the art, joints are typically used in conjunctionswith links to form a robot arm. The configuration of each robot arm canvary greatly depending on the design specifications which typicallyinclude such things as reach, weight of payload to weight of arm,operational environment, dexterity, human machine interfaces, accuracyand repeatability, and control methods. An example of an arm which usesthe joint modules of FIGS. 1 to 7 is shown in FIG. 8. Arm 70 includestwo joint module 10 as the wrist, two joint module 60 as the elbow andtwo joint module 62 with fork connector 64 as the shoulder. The modulesare connected with links 72. As can be seen from the drawing oneadvantage of these joints is that there is no external cabling. This isadvantageous as it reduces the risk of the cabling getting caught onsome unknown projection. Note that in the embodiments shown in FIGS. 1to 8 the joints have internal cabling. As described above, since thehousing 16 provides electromagnetic shielding the cables can be lighterand more bendable since the cables do not need to include shielding orshielded connectors.

The modules can be used with links 72 to form a multi degrees of freedomrobotic arm 70. One embodiment of the arm 70 has six degrees of freedomand a reach of 2250 mm. The arm has a mass of 38 kg and a payloadcapacity of 20 kg. The arm consists of a fork connector 64, shouldermodule 62, lower link 72, elbow module 60, upper link 72 and a wristmodule 10.

Referring to FIGS. 9 to 16, a two joint module is shown generally at 80.Module 80 includes a first joint 82, a second joint 84 and a modulehousing 86.

The first joint 82 includes a first motor 88, a first gearhead 90 and afirst drive 92. By way of example the first drive may be a harmonicdrive. The first motor 88 and first gearhead 90 may be incorporated inthe same unit 94 as shown herein. The first motor and gearhead may alsoinclude an incremental encoder 91. The incremental encoder 91 measuresrelative rotational position of the motor and from the rate of change ofthe relative rotational position the speed of the motor is determined.The position of the motor is determined prior to the gearhead. The firstjoint also includes an absolute encoder 96 which determines therotational position of the output after all of the gears. The absoluteencoder is used to determine the position of the link.

The first joint 82 has a first joint axis 98. The first motor 88, firstgearhead 90, first incremental encoder 91, first drive 92 and firstabsolute encoder 96 are concentric with the first axis 98. The firstmotor 88 has a first motor axis.

The second joint 84 includes a second motor 100, a second gearhead 102,a second incremental encoder 103 and a second drive 104. The seconddrive or motor 104 may be a harmonic drive. The second motor 100, secondgearhead 102 and second incremental encoder 103 may be incorporated inthe same unit 106 as shown herein. The incremental encoder 103 measuresrelative rotational position of the motor and from the rate of change ofthe relative rotational position the speed of the motor is determined.The position of the motor is determined prior to the gearhead. Thesecond joint also includes an absolute encoder 108 which determines therotational position of the output after all of the gears. The absoluteencoder is used to determine the position of the link. A worm gear 112connects the second motor, gearhead and incremental encoder combination106 to the second drive 104. This allows the motor and gearheadcombination 106 to be positioned perpendicular to the second joint axis114. The positioning of the motor and gearhead combination 106 in thisfashion allows for a compact two joint module.

The second joint 84 has a second axis 114. The second drive or motor 104has a second motor axis. The second drive 104 and second absoluteencoder 108 are concentric with the second axis 114. The second motor,gearhead and incremental encoder combination 106 are perpendicular tosecond axis 114. The second axis of the second motor, gearhead andincremental encoder combination 106 is parallel to the first axis of thefirst motor, gearhead and incremental encoder combination 98.

Electronic modules are operably connected to for each of the first joint82 and the second joint 84. The electronic modules are located in acontrol unit (not shown). The electronic modules transmit information inregard to the movement of the joint and control the first motor 88 andsecond motor 100 accordingly. Each electronic module includes interfacesfor all of the sensors such as the incremental encoders, absoluteencoder, and output from torque sensor amplifier, and is capable ofdigitizes all sensor information. Each electronic module includes powerconnections.

The module housing 86 includes first output plate 120 and a secondoutput plate 122. The first output plate 120 and second output plate 122are adapted for mechanical external connections. The module housing 86also includes a housing box 124. The housing box 124 acts as astructural support portion and first joint 82 and second joint 84 areattached thereto. The module housing 86 also includes a first motorcover 126 and a second motor cover 128. The first motor cover 126 alsoincludes and external electronic connector 129. The module housing 86 isrobust enough to transmit forces and torques. As well, the modulehousing 86 enclosures the electronics and motors and protects them fromexternal environment. The module housing 86 acts as an electromagneticshield. The module housing 16 is made from metal and is conductive. Theelectronics modules 48 are enclosed by the housing 16. The housing 16provides electromagnetic shielding.

Module 80 is different from those described above in that it is designedfor external cabling (not shown).

Two joint module 80 may be used as part of a robotic arm 130 as shown inFIGS. 15 and 16. Module 80 is used herein as a wrist module. Module 80may be modified to be used as an elbow module 132. As well, module 80may be scaled up to accommodate different loads.

Elbow module 132 is a two joint module that includes a first joint and aprismatic or linear joint. Module 132 is used herein as an elbow module.Module 132 is an alternative implementation of a two joints. Module 132may be modified to be used as a wrist module 80 or a shoulder module134. The first joint of module 132 may be modified and implemented asthe first joint in combination with a second joint. A prismatic orlinear joint of module 132 may be modified and implemented with secondjoint. Module 132 shares a common structural element in which both thefirst joint and the prismatic are attached.

More specifically two joint module 132 includes a first joint 138 and alinear or prismatic joint 140. The first joint 138 includes a firstmotor 142, a first gearhead 144 and a first drive 146. By way of examplethe first drive 146 may be a harmonic drive. The first motor 138 andfirst gearhead 140 may be incorporated in the same unit 148 as shownherein. The first motor and gearhead may also include an incrementalencoder 150. The incremental encoder 150 measures relative rotationalposition of the motor and from the rate of change of the relativerotational position the speed of the motor is determined. The positionof the motor is determined prior to the gearhead. The first joint alsoincludes an absolute encoder 152 which determines the rotationalposition of the output after all of the gears. The absolute encoder isused to determine the position of the link.

The first joint 138 has a first axis 154. The first motor 142, firstgearhead 144, first incremental encoder 150, first drive 146 and firstabsolute encoder 152 are concentric with the pitch axis 154.

The second joint 140 is a linear or prismatic joint includes a firstmotor 156, a first linear actuator 158. The second joint 140 has asecond axis 160. The second motor 156 and second linear actuator 158 areconcentric with the second axis 160.

The module housing includes a module base 162 and the first joint 138and second joint 140 are attached thereto. The module housing furtherincludes a first motor cover 164, a second motor cover 166 and anactuator cover 168 all of which include electromagnetic shielding. Anexternal cable guide 170 is attached to first motor cover 166. Externalelectronic connectors 172 are attached to the external cable guide 170,first motor cover and second motor cover. The external electronicconnectors 172 are operably connected to the first joint 138 and thesecond joint 138.

The two joint modules 80 and 132 may be used in robotic arms. An exampleof a robotic arm 130 is shown in FIGS. 16 and 17. The modules can beused with a link 136 to form a multi degrees of freedom robotic arm 130.One embodiment of the arm 130 has six degrees of freedom and a reach of1130 mm. The arm has a mass of 20 kg and a payload capacity of 20 kg.The arm consists of a shoulder and turret joint 134, a shoulder joint135, a link 136, an elbow and prismatic module 132 and a wrist module80.

By way of example only the chart below shows the torques that can begenerated by the specific joints shown herein. It will be appreciatedthat the motor size and gear ratios can be varied to achieve thespecific torque that is required for a specific application.

MOTOR JOINT POWER (W) GEAR RATIO TORQUE (NM) Turret 12 38400:1 73Shoulder 25 59200:1 258 Elbow Module 132 Elbow First Joint 12 50560:1123 Elbow Second 4.8 not applicable 200N Linear Joint Module 80 WristFirst Joint 12 20480:1 33 Wrist Second Joint 15 38000:1 20

The elbow module 132 and shoulder module 134 may be connected with alink 136.

Generally speaking, the systems described herein are directed to twojoint modules. As required, specific embodiments are disclosed herein.However, the disclosed embodiments are merely exemplary, and it shouldbe understood that the disclosure may be embodied in many various andalternative forms. The Figures are not to scale and some features may beexaggerated or minimized to show details of particular elements whilerelated elements may have been eliminated to prevent obscuring novelaspects. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present disclosure. For purposes of teachingand not limitation, the illustrated embodiments are directed to twojoint modules.

As used herein, the terms “comprises” and “comprising” are to construedas being inclusive and opened rather than exclusive. Specifically, whenused in this specification including the claims, the terms “comprises”and “comprising” and variations thereof mean that the specifiedfeatures, steps or components are included. The terms are not to beinterpreted to exclude the presence of other features, steps orcomponents.

What is claimed is:
 1. A robotic arm comprising: a first link havinginternal link cables extending from one end to an opposed end thereof; afirst joint operably connected to the first link at one end thereof; thefirst joint having a hollow drive shaft, an off axis drive and a firstjoint motor and first joint internal cables extending through the hollowdrive shaft; a second joint operably connected to the first link, thesecond joint having an active side, a passive side with electronicconnectors, second joint internal cables, and a second joint motor andthe active side being mechanically connected to the first link; andwherein the link cables and the first joint cables are operablyconnected, and the electronic connectors of the passive side on thesecond joint are operably connected to the link cables.
 2. The roboticarm of claim 1 wherein the first joint and the second joint each furtherincludes a gearhead and a drive operably connected to the respectivemotor.
 3. The robotic arm of claim 2 wherein each drive is a harmonicdrive.
 4. The robotic arm of claim 3 wherein each joint further includesabsolute encoders and incremental encoders operably connected to therespective motor.
 5. The robotic arm of claim 4 wherein each jointfurther includes torque sensors.
 6. The robotic arm of claim 5 whereinpower of the joint is in a range between 5 and 50 W, and torque of thejoint is in a range between 20 and 826 N/m.
 7. The robotic arm of claim6 wherein the first motor and gearhead is a combination motor andgearhead.
 8. The robotic arm of claim 7 wherein one of the first jointand second joint has a joint axis and the motor has a motor axis andmotor axis is at an angle to joint axis.
 9. The robotic arm of claim 8wherein the angle is perpendicular.
 10. The robotic arm of claim 9wherein the other of the first motor and the second motor has a motoraxis and wherein the one motor axis is parallel the other motor axis.11. The robotic arm of claim 10 wherein each joint further includes ahousing and the housing acts as an electromagnetic shield.
 12. Therobotic arm of claim 1 further including a second link operablyconnected to one of the first joint and the second joint.
 13. Therobotic arm of claim 12 wherein the first joint and the second joint area combination two joint module.
 14. The robotic arm of claim 13 furtherincluding a third joint and a fourth joint each operably connected tothe second link.
 15. The robotic arm of claim 14 wherein the third jointand the fourth joint are a combination two joint module.
 16. The roboticarm of claim 15 further including a fifth joint and a sixth joint. 17.The robotic arm of claim 16 wherein the fifth joint and the sixth jointare a combination two joint module.